1. Field of the Invention
The present invention relates to a system for determining the position of a mobile communication terminal, and more particularly, to an apparatus for determining the position of the mobile communication terminal, in which a satellite signal and a mobile communication signal are used, and a method therefor.
2. Description of the Background Art
A conventional method for determining the position of a mobile communication terminal (hereinafter, a mobile terminal) is divided into a method, in which a global positioning system (GPS) is used, and a method, in which a mobile communication signal is used. According to the method, in which the GPS is used, the position of the mobile terminal is calculated using a GPS satellite signal. According to the method, in which the mobile communication signal is use, the position of the mobile terminal is calculated by measuring the reception angle and the delay time of a signal delivered by the mobile terminal.
FIG. 1 shows a conventional position determination system, in which the GPS is used.
As shown in FIG. 1, the conventional position determination system, in which the GPS is used, includes a mobile terminal 101, in which a GPS engine 101a is loaded, a base station 102 for transmitting data to and receiving data from the mobile terminal 101, a GPS receiver 105 for receiving the transmission signal of a GPS satellite 104 and outputting the error compensation data of the GPS satellite signal and information related to the GPS satellite 104 such as a satellite number, a satellite orbit, Doppler information, and a navigation message, and a position calculation server 106 for transmitting the error compensation data and the satellite information that are output from the GPS receiver 105 to the mobile terminal 101 and calculating the position of the mobile terminal 101 using the pseudo range transmitted from the mobile terminal 101 through a network 103.
The operation of the conventional position determination system, in which the GPS is used, of the above structure will now be described with reference to the attached drawings.
The GPS engine 101a that is built-in the mobile terminal 101 requests the GPS satellite information to the position calculation server 106 through the base station 102 and the network 103.
At this time, the GPS receiver 105 connected to the position calculation server 106 receives the transmission signal of the GPS satellite 104, measures data for correcting the error included in the GPS satellite signal and the GPS satellite information such as a satellite orbit parameter, the Doppler information, and the navigation message, and periodically outputs the data and the GPS satellite information to the position calculation server 106.
When the GPS satellite information is requested by the GPS engine 101a, the position calculation server 106 transmits the GPS satellite information stored in a database (DB) to the GPS engine 101a through the network 103 and the base station 102. The GPS engine 101a calculates the pseudo range between the mobile terminal 101 and the GPS satellite using the transmitted GPS satellite information such as a receivable satellite number, the satellite orbit parameter, the Doppler information, and the navigation message, measures the time information of the GPS satellite signal, and transmits the pseudo range and the time information to the position calculation server 106 together with a position calculation request signal.
Therefore, according to the position calculation request of a mobile terminal 301, the position calculation server 106 corrects the pseudo range using the error correction data stored in the DB and calculates the position of the mobile terminal 101 using a triangular survey.
FIG. 1 shows the conventional position determination system, in which the mobile communication signal is used.
As shown in FIG. 1, the conventional position determination system, in which the mobile communication signal is used, includes a plurality of signal measuring apparatuses 202-1 installed in a base station 202, the signal measuring apparatuses 202-1 for measuring the reception angle and the delay time of the signal transmitted from a mobile terminal 201, a mobile communication signal server 204 for storing the reception angle and the delay time of the mobile communication signal transmitted by the signal measuring apparatuses 202-1, and a position calculation server 205 for reading the reception angle and the delay time of the mobile communication signal from the mobile communication signal server 204 according to the request of the mobile terminal 201, to thus calculate the position of the mobile terminal 201.
The operation of the conventional position determination system, in which the mobile communication signal is used, of the above structure will now be described.
The signal measuring apparatuses 202-1 receive the transmission signal of the mobile terminal 201, measure the reception angle and the delay time of the transmission signal, and transmit the measured reception angle and delay time together with identifier information and reference time information. At this time, times between the signal measuring apparatuses 202-1 must be synchronized.
Therefore, the mobile communication signal server 204 receives the reception angle and the delay time from the signal measuring apparatuses 202-1 through a network 203 and stores the reception angle and the delay time by mobile terminals, measuring times, and signal measuring apparatuses (or base stations).
When the position of the mobile terminal 201 requests the position calculation server 205 to calculate the position thereof, the position calculation server 205 obtains the reception angle and the delay time of the mobile communication signal from the mobile communication signal server 204 and calculates the position of the mobile terminal 201.
In general, according to the conventional position determination method, in which the GPS is used, it is possible to calculate the correct position of the mobile terminal only when four or more GPS satellite signals are received due to a time error during the triangular survey. In the downtown, it is possible to measure only a small number of GPS satellite signals because there exist various elements that deteriorate the visibility of the GPS satellite signal such as skyscrapers. In particular, it is not possible to smoothly receive the GPS satellite signal inside buildings, where the GPS satellite cannot be seen. Therefore, according to the conventional position determination method, in which the GPS is used, the position of the mobile terminal cannot be correctly determined in the downtown or inside the buildings.
According to the conventional position determination method, in which the mobile communication signal is used, it is possible to calculate the correct position only when the reception angle and the delay time of the mobile communication signal are received from three or more signal measuring apparatuses. In the downtown, it is possible to easily receive the mobile communication signal from three or more signal measuring apparatuses because there exist a large number of base stations. However, in a highway and the country, it is not possible to smoothly receive the mobile communication signal because there exist a small number of base stations. Therefore, according to the conventional position determination method, in which the mobile communication signal is used, it is not possible to determine the position of the mobile terminal in the highway and the country.
Also, in the downtown, errors increase in processes of propagating the transmission signal of the mobile communication signal because the transmission signal propagates through multiple paths. Therefore, in the downtown, more errors are found in the conventional position determination method, in which the mobile communication signal is used, than in the position determination method, in which the GPS is used.